1. Field of the Invention
This invention relates to a method for supplying coal gas to a large industrial consumer, and more particularly to supplying coal gas to a smelting works, wherein a coal gas is produced in an iron bath reactor from solid or liquid carbon carriers by the addition of oxygen drawn in gaseous form from an oxygen line. The coal gas so produced is conducted to consumers such as industrial furnaces, heaters and pickling solutions. The invention also relates to a method for the coal gas supply and fuel gas supply in a smelting works or in another large consumer of fuel gas.
2. Description of the Prior Art
Methods for coal gasification in an iron bath reactor on which this invention is based are, for example, known from West German Patent No. 2,520,938 and West German Unexamined application Nos. 30 31 680 and 31 33 575. Furthermore, a coal gasification method is described in West German Unexamined application No. 29 52 434. The use of coal gases produced from such methods for smelting-works-owned or external consumers is described in West German Unexamined application No. 27 33 790. According to this method, vapor is produced from the sensible heat contained in the generated coal gas and with which a generator is operated. The purified, scrubbed, and cooled coal gas is optionally available to consumers in the smelting works, and the like, in addition to being used in an iron bath reactor for injection. To this end, the coal gas is stored in a gas tank.
If there is sufficient coal gas production, all the smelting-works-owned gas consumers, such as, for example, industrial furnaces, power stations, mordants, etc., can be operated with coal gas instead of with natural gas or instead of with petroleum as typically used in the past. However, in the method known from West German Unexamined application No. 27 33 790 for the coal gas supply of a smelting works, a continuous supply is not warranted. Coal gas production in an iron bath reactor is necessarily subject to downtime and cold time interruptions. After a certain time, the iron bath has to be emptied and the reaction vessel relined. During this downtime period, coal gas production in the iron bath reactor is not possible.
In order to be able to maintain a continuous coal gas supply, an interconnecting gas supply network with other smelting works or with other coal gas producers would be required, or several independent coal gas producing units would have to be available in the smelting works. However, such interconnecting supply networks are expensive. Moreover, several iron bath reactors are less economical than a large reactor which is sufficient for all the quantity of coal gas required. Therefore, in the final analysis, the coal gas supply of a smelting works or of another large consumer of coal gas typically will occur in an insular operation, or "in house" as is usually the case with a blast-furnace gas supply.
Thus, in accordance with the teachings of West German Unexamined application No. 27 33 790, the connected external gas consumers must be supplied from a quantity of coal gas stored in a gas tank. However, quantities of coal gas that become available or are required are very large. Taking into consideration that a smelting works aims at a coal gas production rate of approximately 120,000 m.sup.3 /hr., gas tanks are needed with extremely high volumes and which therefore require a large capital outlay and take up considerable space. During a disturbance in the smelting process lasting more than a few hours and during repair work on the unit, stocking up the amount of coal gas needed by the external consumers during the disturbance in accordance with the teachings of West German Unexamined application No. 27 33 790 is not economically feasible.
Therefore, during smelting works downtime the fuel consumers are normally supplied within the framework of an emergency supply by means of other energy carriers, more particularly natural gas. However, during such downtime there is an obvious difference in the consumption of natural gas. That is, over relatively long periods of time during active smelting works operations practically no natural gas is consumed, whereas during downtimes in coal gas production considerable quantities of natural gas are needed. Under these conditions, natural gas is a relatively expensive energy carrier. Moreover, separate gas lines or separate burners are needed. Thus, a switch must be made from coal gas to natural gas on the premises of the fuel consumer. Although a natural gas reservoir that would enable a virtually continuous fuel consumption would have relatively small dimensions compared to a coal gas reservoir, it still would have to be so large and, hence, so expensive as to be uneconomical. Storing in underground caverns is possible only under certain geological conditions which are not present at every site. In either case, in addition to the high costs in terms of capital outlay, considerable energy costs are incurred for the compression work for storing.